Dehydrating apparatus



March 15, 1966 J. H. FORKNER 3,239,946

DEHYDRATING APPARATUS Filed Dec. 6, 1961 3 Sheets-Sheet 2 f 500 4e/75afe Wea/77 MQA March l5, 1966 1. H. FoRKNER DEHYDRATING APPARATUS 3Sheets-Shea?I 3 Filed Dec. 6, 1961 r. m f W@ I 7 J w. M M v 0//- \\/wkWH 2 u. o/ ya WZ l E 'Il J E HHHJIC I l l m l n IF ML ,i n: O. al W. W

United States Patent O 3,239,946 DEHYDRATING APPARATUS .lohn H. Forkner,Fresno, Calif., assignor to The Pillsbury Company, Minneapolis, Minn., acorporation of Delaware Filed Dec. 6, 1961, Ser. No. 157,449 11 Claims.(Cl. Sti-69) This is a continuation-in-part of application Serial No.78,977, tiled December 28, 1960, now abandoned.

This invention relates generally to apparatus for the dehydration ofvarious moist food materials. More specically, it pertains to apparatusfor carrying out dehydration methods of the type in which the moist foodor similar organic materials are introduced into a bath of hot oil,under partial vacuum.

In my copending application, Serial No. 157,538 tiled December 6, 1961,entitled Dehydrating Method, Product and Apparatus, there is disclosed amethod for the dehydration of a wide variety of moist food materials,involving contacting frozen food particles with hot oil under a partialvacuum. In typical instances the initial temperature of the oil may bewithin the range of 240 to 600 F. The applied partial vacuum can be ofthe order of 22 to 28 inches mercury column. Initial rapid heat transferfrom the hot oil to the moist food material rapidly drops thetemperature of the oil over a short period of the order of from 1/2 to 4minutes. Also initial contact of the frozen material with the hot oilcreates a foam-like medium of expanded volume comprising a mixture ofwater vapor and foam, which medium envelops the material beingdehydrated. Thereafter the foam-like medium subsides and the dehydrationcycle is completed at a lower temperature level, as for example, withinthe range of from 170 to 230 F. At the end of the dehydrating cycle thematerial may be treated as by centrifuging, to eliminate excess oil. Inmost instances centrifugng is applied. while the partial vacuum ismaintained. Thereafter the product may be impregnated with certainmediums, to impart desired characteristics. The method just describedproduces high grade dehydrated products, which are superior to productsdehydrated by ordinary vacuum evaporation or other conventional methods.

In general it is an object of the present invention to provide novelapparatus for carrying out dehydration methods of the above character,whereby such methods are adapted to commercial operations.

Another object of the invention is to provide an improved apparatus ofthe above character which provides effective control over thedehydrating cycle.

Another object of the invention is to provide apparatus capable ofcentrifuging the material under an applied partial vacuum.

Further objects and features of the invention will appear from thefollowing description in which the preferred embodiments have been setforth in detail in conjunction with the accompanying drawings.

Referring to the drawings:

FIGURE l is a ilow diagram illustrating the general steps employed in mymethod;

FIGURE 2 is a ow diagram like FIGURE 1, but with additional proceduralsteps such as are employed tin utilizing the apparatus of FIGURE 3;

FIGURE 3 is a schematic side elevational view, partly in section,illustrating apparatus for carrying out the method of FIGURES 1 and 2;

FIGURE 4 is a side elevational view, partly in section, showing anotherembodiment of the apparatus;

FIGURE 5 is a detail in section, showing a part of the adjustablescreen; and

FIGURE 6 is a detail, partly in section, illustrating another embodimentof the invention in which centrifuging can be applied while partialvacuum is being maintained..

Referring to the simplified flow diagram of FIGURE l, I have indicatedhydrous food material being prepared in step 10 for the subsequentdehydration cycle. In general, the source material may be various fruitsor berries, vegetables, meats, fowl, sea food, condiments, cereal grain,formulated bakery products, or moist formulated mixtures of the same. Aspointed out in said copending application, preparation may includewashing, peeling, pitting, and cutting into masses or particles ofsuitable size for further treatment. Also, it may include somepreliminary processing, such as drying by contact with warm drying air,pre-cooking, pickling or so-called candying or glace treatments whichimpart a sugar-syrup content. In some instances dried or semi-driedmaterial may be rehydrated before freezing. Freezing may be carried outby chilling to temperatures of the order of '-20 to {-10 F., as iscommonly practiced in the frozen food industry. In typical instances,the individually frozen particles may measure from 1A; to 5A; inch inthickness, and preferably the weight of each particle does not exceedabout l() gms. If the particles are in the form of shreds or strings,they may be from 1,@4 to 3/16 inch in thickness.

In step 11 the prepared material is shown being contacted by hot oilunder partial vacuum, for dehydration. As will be presently explainedduring the initial phase of moisture removal, the material is envelopedin a foam-like medium comprising a mixture of water vapor and oil.Toward the end of the initial phase the foam-like medium subsides andthereafter the material is immersed in a liquid body -of hot oil. Theoverall length of the dehydration cycle to reduce the moisture contentto a predesired value (e. g. from `1/2 to 5%) depends on variousfactors, including the temperature of the oil, initial temperature ofthe material, the ratio between the weight of the charge of frozenmaterial and the weight of the oil employed, the difference between theinitial temperature of the material and the initial oil temperature, thevalue of the partial vacuum, the moisture content of the original sourcematerial, and the size of the particles. At the end of a typicaldehydration cycle, as indicated in step 12, the bulk of the free oil isremoved or separated from the material before the vacuum is broken. Theremaining dehydratedproduct may be the iinal product as indicated.Assuming, however, that it is desired to remove some of the retainedfree oil, the product is subjected to centrifuging in step 13, wherebysome further oil is removed to form the final product.

Instead of using the same oil throughout the cycle, a clarified oil, ata proper temperature, may be substituted for a predetermined portion ofthe oil used in the initial phase of the cycle. In such an event, aportion of the rst oil is drained from the treatment tank at a point inthe cycle where it is desired to modify the body of the oil, as forexample, after the iirst intial phase during which rapid evaporationtakes place, -and thereafter a clarified -hot oil applied at -atemperature such that the aggregate body of oil attains a temperaturelevel of the order of F., after which the dehydrating cycle proceeds tocompletion. In some instances more than one such modi- Ification of theoil body can be employed during the complete cycle. In most instancesthe temperature of the oil at the end of the first initial phase tend-sto drop below 195 F. By introducing a predetermined amount of oil at atemperature above 195 F., the temperature of the oil can be quicklyraised to the desired level (eg. 195 F.) for continuing the cycle.

In some instances it is desirable to employ the procedure shown inFIGURE 2, wherein the food product to be treated is subjected topreliminary preparation 20 in the same manner as described withreference to FIGURE 1. Thereafter in step 21, the frozen material ischarged into a body of hot oil under partial vacuum. Dehydrationproceeds as in FIGURE 1, with an initial phase during which the materialis enveloped and dispensed in a foam-like medium of vapor and oil, and afollowing phase in which the material is immersed in a liquid body ofoil. In step 22 oil is withdrawn from the dehydrated material, and whileapplication of partial vacuum is continued, the product is subjected tocentrifuging in step 23 to remove excess oil. As indicated, in step 24the vacuum is broken and the final product discharged. Centifugingbefore the vacuum is broken is desirable because it results in a finalproduct having a lower oil content, and having certain desirableproperties as described in said copending application Serial No. 157,538filed simultaneously herewith. Also it tends to prevent crushing of thecells by atmospheric pressure. yRemoval of the product from the oil bodyunder partial vacuum, is accompanied by a cooling of the product, due tofurther evaporation of moisture. Toward the end or immediately followingcentrifuging, a somewhat higher partial vacuum can be applied for ashort interval to accentuate evaporative cooling by further moistureremoval. The higher vacuum causes some increase in volume and coolingsets the cell structure and solidies the oil, thus providing rigiditybefore the vacuum is broken.

The apparatus schematically illustrated in FIGURE 3 is suitable forcarrying out the procedure outlined in FIG- URE l. The tank 31 is ofsufficient size to contain a measured quantity of hot oil. It will benoted that this tank is relatively high in comparison to its diameter.In a typical operation the ybody of oil within the tank at the start ofa dehydrating cycle occupies only the lower oneeighth of the tank. Thesealed cover 32 of the tank is shown connected to an evacuating conduit33. The evacuating equipment may include suitable condensing means forcondensing moisture (eg. a wat-er spray condenser having a barometriccolumn) and suitable vacuum pumping means.

Within the upper part of the tank there is a horizontally disposedbarrier screen 34 which is suspended in such a manner that it can bepositioned at a desired level. It is provided with a perforated rim 36of substantial height, and with a bail 37 which is carried by suitablesupporting means such as the cables 38. The upper ends of these cablesare wrapped about a winch shaft 39, which has an exterior operatingcrank 41. At a proper time in the dehydrating cycle the screen 34 islowered below the oil y level, thereby (by its weight) retainingparticles of material being dehydrated submerged and in good heattransfer contact with the oil. Rim 36 is of sutiicient height to extendabove the Aoil surface, thus preventing particles being dehydrated fromfinding their way about the edges of the screen 34 and upon top of thesame.

The means employed for charging the tank can consist of a heat insulatedor refrigerated hopper 42 which is provided with the sealed removablecover 43. A feed screw housing 44 communicates with the lower end ofhopper 42, and with the interior of the tank 31 through one side wall.The feed screw 45 is operated by suitable means such as the electricalmotor 46. The tank end of housing 44 may be provided with a closuremeans 47, such as one of the hinged flap type as illustrated.

The side walls of the tank preferably are provided with heat insualtingmeans or a steam jacket (not shown) to minimize loss of heat from thebody of oil.

The lower portion of the tank 31 is provided with a downwardly extendingopening 4S which is normally closed by the discharge door 49. This dooris shown hinged at 5i), and may be power operated by suitable means suchas the hydraulic jack 51. When closed, this door can be clamped bysuitable means such as the clamping screws 52. The door 49 is dished orformed las a vessel, and its interior communicates with the exteriorpipes 53, 54, through the swing joint 55. The upper side of thedischarge door is provided with a screen 56 which supports thedehydrated material while oil is being removed.

FIGURE 3 shows suitable heating means for heating oil being supplied tothe tank 31 to a desired tempera-` ture level (e.g., from B25-440 F.).Thus, two heaters 61 and 62 are provided, with oil being supplied to theheater 61 by pump 63 and pipe 64. From heater 61 the oil passes throughpipe 66 to the heater 62, and then through pipe 67 to the tank 31. Steamis shown being supplied to heaters 61 and 62 by pipes 68 and 69. Heater62 serves to elevate the oil temperature to a desired level and inaddition can be used to heat the oil during a dehydrating cycle. Becausemany hot oils tend to deteriorate at temperatures in excess of 200 F.,when in contact with air, it is desirable for the oil in heater 62 to beunder vacuum. Thus, I employ a heater of the open kettle ty-pe asschematically indicated, which may include the open kettle 62a enclosedwithin the shell 62h. Steam from pipe 68 passes through the heating coil612C. A small amount of steam is shown being bled into kettle 62athrough pipe 90, thereby providing agitation. Pipe 70a connects shell62b to an evacuating system. The tank or kettle 62a should havesufficient capacity to supply at least one charge of oil to tank 31.

A storage and oil reclaiming system 71 is shown connected to the pipingdescribed above, whereby oil from a preceding cycle can be sent fromtank 31 to storage, and whereby reclaimed or reconditioned oil can besupplied for the next dehydrating cycle, or at the end of the initialphase of the cycle. Briefly the storage and oil retaining system canconsist of suitable storage tanks to receive used oil, together withfiltering and centrifuge means for removing solid and liquid fractionsderived from the food material being processed. Also the storage andreclaiming system can be adapted t0 receive fresh makeup oil, andstorage tanks for holding oil in readiness for further use.

Operation of the apparatus described above is as follows: Valves 72 and76 are closed and cover 43 opened to receive a charge of material, afterwhich cover 43 is closed. Tank 31 and hopper 42 are now evacuated. Withvalves 74, 75, 76 and 80 open, and valves 73 and 77 closed, pump 63withdraws oil from storage and delivers it serially through the heaters61 and 62, whereby the temperature lof the oil is raised to the leveldesired. This oil is supplied to the tank 31 until the level reaches apredetermined height (eg. about oneeighth full as indicated). Then motor46 is placed in operation whereby the food material is quickly deliveredinto the upper part of tank 31 and dropped into the body of hot oil. Atthat time the partial vacuum applied can for example be within the rangeof 26 to 28 inches mercury column.

Rapid evolution of moisture occurs immediately as the particles arereceived in the body of hot oil and a vapor-oil foam is created, whichexpands upwardly and envelops and disperses the particles. This isaccompanied by considerable agitation and by a large increase in volume.The foam level rises about 3 to l0 times the vnormal initial oil level.During this fpart of the cycle the particles are not restrained and maymove freely in tbe tank. A small amount of oil tends to be carried thethe vapor ilow to the condenser, where it mixes with the condenserwater. Such oil can be recovered by subjecting the condenser water toseparation, as by flotation. Screen 34 at this time is in the upper partof the tank and interposed in the path of vapor ow, where it tends toprevent carry over of particles being dehydrated and to inhibit carryover of foam and oil.

There is an immediate and rapid temperature drop during the initialphase of the cycle which reduces the temperature of the oil to asubstantially lower value,

(eg. 13G-230 F.). For the remainder of the cycle it is desirable tomaintain a lower temperature level (eg. l70-230 E). The extent oftemperature drop in `the first phase can be reduced to some extent bysupplying heat to the oil, as for example by supplying steam to aheating jacket `on the tank, or by circulating the oil through theheater 62 by having valves 72, 76 and 77 open, and valves 74, 73, 75 andSi) closed. Also the oil and particles being dehydrated can be quicklyheated to a desired temperature level at or near the end of the iirstphase, as by blending in hot fresh oil as will be subsequentlyexplained.

During the dehydrating cycle and while the vacuum is maintained theparticles tend to be buoyant. Toward the end of the initial phase of thedehydrating cycle and as the oil level subsides, the buoyant particlestend to float as a mat upon the surface of the oil. At that time thescreen 34 is l-owered to a position in which it is below the surface ofthe oil, whereby the particles are held submerged below the surface ofthe oil for good heat transfer.

After the initial phase of the cycle, some of the oil first contacted bythe material being dehydrated may be withdrawn through pipe S3, and hotclarified oil substituted. The amount withdrawn may vary over widelimits. In general as the withdrawal approaches 100 percent of the oilpresent, the method and the product during the remaining part of thecycle are less affected by any characteristics of the initial oil thatare acquired in the initial phase of the cycle. The temperature of thefresh hot oil is :such that when mixed with the material and the oilpermitted to remain, a temperature is attained that is suitable for therest of the cycle. rIhis has the advantage of contacting the materialwith clarified oil for the latter phases of dehydration, instead ofmaking use of oil containing solids derived from the material 4beingdehydrated in both the initial and subsequent dehydrating phases.Furthermore this procedure applies heat to clarified oil, and avoidssupplying heat to oil containing solids derived from the product, as byconventional heat exchange means (eg. steamjackets or tubular heaters).The latter procedure causes formation of incrustations on the heatingsurfaces, thus requiring frequent shutdown for cleaning. In addition ittends to burn solids derived from the product, such as sugars, dextrins,etc., thereby contaminating the oil. Such contamination detrimentallyaffects the product, as by imparting a burned `flavor 'and causing adarkening in color. In general, therefore, substitution of clarified oilserves to reduce the amount of soilds present in oil used to continuethe cycle, it provides a means to impart heat to the oil without thedisadvantages of conventional heating means, and because of both of theforegoing, it minimizes ilavor changes and discolorations which mightoccur if burned solids were permitted to accumulate in the oil. yInaddition the substituted oil may differ from the initial oil and may forexample have a higher melting point or may impart a desired flavoring.If desired, more than one modification of the oil can be made before thedehydration cycle is completed.

At the end of the dehydrating cycle, pump 63 is again placed inoperation, and with valves '72 and 73 open, the valves 75, 77 and 74closed, oil is withdrawn through pipe 54 and from the lower door 49below the screen 56. The used oil is sent to the storage `and reclaimingsystem 7l, where it is treated to centrifuging and filtration and thenstored for use in a succeeding cycle. In the event the oil has notbecome seriously contaminate-d by use in one cycle, it may in thetreatment of some products be stored .and then returned through th-eheaters 61 and 62 for the next cycle, or it may be lblended with varyingamounts of fresh or reclaimed oil, .and reused. By pumping out oil fromthe door 49 below the screen 56, substantially all of the free oil canybe removed from below the floating product and drained from the productafter the latter deposits on screen 56. Only a minor amount of oilremains upon the surfaces of the particles, and within some of thepores. When the product is separated from the body of oil under apartial vacuum, it cools because of continued evaporation of moisture.At this time a somewhat higher vacuum can be applied for a shortinterval to remove further moisture and to accentuate such evaporativecooling. Thereafter the partial vacuum within the tank 31 may be brokenby connecting conduit 33 to the atmosphere, and door 49 opened todischarge the dehydrated material into the vessel 57. The dehydratedmaterial can then be subjected to centrifuging for the removal lof someof its retained oil in the manner described in said copendingapplication.

The apparatus described above can be altered as shown in FIGURE 4, tocarry out the method outlined in 'FIG- UR'E 2. Thus, in this instancethe lower end of the tank 31 is provided with a valve 78, as forexample, one of the butterfly type. Below this valve there is a hingehousing 79 which contains a centrifuge basket 81, adapted to be driventhrough suitable means such as the exterior pulley wheel S2. Below thebasket 8l the housing connects with the flexible tubing S3, which inturn connects to the pipe 53a leading to the pump 63. The housing 79 mayhave a separate -connection with evacuating means.

With the equipment of FIGURE 4, the butterfly valve '78 remains closedduring the dehydrating cycle, whereby the material being dehydrated isretained within the tank 31. At the end of the cycle the butterfly valveis opened, without releasing the partial vacuum, whereby oil and thedehydrated material may enter the centrifuge basket 31. Pump 63 is nowplaced in operation to withdraw oil through the pipe 83 and theperforations of the centrif-uge basket, until all of the oil has thusbeen removed. While application of partial va-cuum is maintained thecentrifuge is placed in operation to remove some remaining oil, and thisis again removed through the pipe 83. Thereafter the vacuum is brokenand housing 79 swung downwardly to permit removal of the dehydrated and'centrifuged material.

FIGURE 6 shows an embodiment in which a different means is provided inplace of the screen 34., to retain the material being dehydrated belowthe surface of the oil for the latter phase of the dehydrated cycle.Thus, in this instance in place of the screen 34, which can be raised orlowered, the tank 9i intermediate its ends is equipped with a screen 92that is pivoted for rotation about .a horizontal axis. When turned to avertical position, from the position shown in solid lines, this screendoes not interfere with passage of particles of material beingdehydrated. When in the position shown it is pervious to oil 'but willretain the material being dehydrated. The centrifuge housing 93 in thisinstance is attached by the coupling flanges 94 to the lower end of tank91, and serves to house the foraminous centrifuge basket 96. rThe rim-97 at the upper end of the basket is arranged to engage a collar 98 ofresilient material, the latter being attached to the lower end of thetank. Pipe 99 is provided for the removal of oil, and pipe 161 may beprovided for introducing an impregnating medium, `such as a liquid orvapor. Pipe 192 normally is closed, but may be opened at the end of thecycle to break the vacuum with dehumidified air, an anhydrous inert gaslike nitrogen, or other treatment gas.

With the apparatus of FIGURE 6 the housing 93 functions as a part of thetank for carrying out the dehydrating cycle. Initially screen 92 is openor in vertical position for free movement of material during the initialphase. Care is taken whereby before the screen 92 is closed, the oillevel is well below its path of movement, whereby particles floating onthe oil will be below the screen. In general, this may require removalof some oil from the lower portion of the tank, until the oil level iswell below the screen. After the screen has been closed, the oil levelis adjusted to a level above the screen, by introduction of additionalclarified hot oil, whereby thereafter the material being dehydrated isretained below the screen and below the oil level.

At the end of the dehydrating cycle, making use of the apparatus shownin FIGURE 6, removal of oil through pipe 99 while the partial vacuum ismaintained permits free oil to drain from the dehydrated material. Aftera short holding period, during which drainage is completed, centrifugebasket 96 is rotated whereby additional oil is removed from thematerial, with this oil being likewise returned to storage through pipe99. A higher vacuum can now be applied for a short interval toaccentuate evaporative cooling. Centrifuging under vacuum serves toproduce products having novel characteristics, as disclosed in said lastmentioned application. After centrifuging has been completed, the vacuumis released, and thereafter the flanged coupling 94 disconnected forremoval of the housing 93 and basket 96. To release the vacuum I preferto use a cool gas of low relative humidity, such as dehumidified air.With some materials it is desirable to employ an anhydrous sterile inertgas like nitrogen, whereby subsequent oxidation is inhibited.Particularly where the product is packaged in a gas like nitrogen, thisprocedure can be employed immediately before the packaging operation.Sterilizing or mold inhibiting gases can be effectively applied to theproduct by using the same procedure, that is by breaking the vacuum withan anhydrous gas like ethylene oxide. Application of a treatment gas tobreak the vacuum is particularly effective because the porous product atthat time has a minimum amount of absorbed and occluded gas, and in theprocess of breaking the vacuum the introduced gas is caused effectivelyto penetrate into the pores or cells of the product.

As previously stated, the apparatus can be employed for the dehydrationof a variety of food materials, including fruits and berries,vegetables, condiments, meats, fowl and seafood. A wide variety offruits can be treated by my method, including fresh apples, peaches,aprieots, pineapple, cherries, bananas, grapes, dates, strawberries,blueberries and the like. Vegetables which are applicable include peas,carrots, potatoes, celery, cabbage, bean sprouts, onion, peppers, sweetpotatoes, corn, cereals and the like. The cereals may include wheat,rice, barley, and malt, fresh or with pretreatment such as milling toremove such fractions as cortex, bran and germs, and preliminary dryingand rehydration. Meats that are applicable include beef, pork, lamb,processed meats such as ham, corned beef, cured pork and the like. As tofowl, reference can be made to chicken, turkey, pheasant, duck and thelike. As to seafood, reference can be made to shrimp, both fresh andcooked, tuna and other fish such as commonly marketed, oysters, clams,lobster, crab and the like. As condiments, reference can be made tomushrooms, water chestnuts, and various spices and herbs.

As disclosed in my aforesaid copending application, a wide variety ofoils and fats can be used. For example, I can employ various oils andfats of vegetable or animal origin. As examples of vegetable oilreference can be made to corn, cotton seed, rice bran, soy, olive,peanut, coconut, sesame, tomato seed and the like. As examples of animaloil, reference can be made to fish oil, lard, butter oil, tallow, andthe like. Generally, it is desirable to use oils or fats which have beenrefined to the point where they do not impart any undesirable odor orflavor to the product. The so-called hydrogenated oils have been usedwith good results, such as hydrogenated shortening fats.

In addition to the oils and fats referred to above. I can employ ediblewaxes that are stable liquids at temperatures of the order employed inmy method. For example, natural or refined beeswax has been used withgood results. Such a wax can be blended in various amounts with asuitable oil or fat, thereby modifying certain physical characteristicsof the oil. Particularly introduction of the wax raises the meltingpoint of the oil and increases its viscosity. Also it provides a mediumwhich is more stable and therefore better adapted for reuse, and whichtends to be absorbed to a lesser extent by the product. Greaterstability of the blended oil tends to increase shelf life and to betterprotect the product against atmospheric moisture. Another example isJojoba wax which can be blended with oil (eg. hydrogenated shortening),and which likewise modifies the oil by increasing the melting point,lowering the smoking point, and making the oil more stable and betteradapted for repeated reuse.

For an explanation of the appended claims the term oil as used thereinis intended to include oils, fats and waxes (all of which are esters offatty acids) and blends thereof, with or without hydrogenation,decolorizing, deodorzing or other refining. Also it includes materialshaving characteristics like oils or fats, which are edible, and whichare stable under the temperatures and partial vacuums involved.

Preferably the oil has a melting point above atmospheric, as for examplefrom 102 to 160 F. Flavor containing oils, such as butter oil or naturalanimal fats (e.g. chicken fat) may in some instances be used to impart adesired fiavoring. Special flavoring ingredients can be inserted in theoil, with retention of some such avoring in material undergoingtreatment. At temperature levels ranging up to 400 F., and with anapplied partial vacuum, the more prominent vegetable and animal oils arenot subject to serious breakdown or changes in their molecularstructure. Certain oils are sufficiently stable for commercial use attemperatures ranging up to about 600 F., in vacuum.

I claim:

1. In apparatus for the dehydration of discrete masses of moistmaterial, tank means adapted to contain a quantity of hot oil, chargingmeans connected to the tank means and operable to introduce saidmaterial into the tank means, evacuating means for placing the interiorof the tank under partial vacuum and serving to evacuate vapors andgases from the tank means, said charging means having a space normallyclosed with respect to the atmosphere and adapted to contain a quantityof material to be introduced into the tank means for dehydration andalso adapted to be in communication with the interior of the tank meanswhereby said evacuating means serves to place both the interior of thetank means and the space of said charging means under partial vacuum,said charging means being operable under such conditions of partialvacuum to feed material from said space into the interior of the tankmeans, and means for removing discrete masses of dehydrated materialfrom the tank means.

2. Apparatus as in claim 1 together with screen means within the tankmeans movable between one position in the tank means in which it doesnot interfere with movement of the discrete masses within the tankmeans, and a second position in the tank means in which it extendsacross the tank means to keep the uppermost level of the massessubmerged in the hot oil.

3. Apparatus as in claim 2 in which said screen means is rotatablewithin the tank means to move the same between said two operatingpositions.

4. Apparatus as in claim Z in which said screen means is movablevertically within the tank means between said two positions.

5. In apparatus of the character described for the dehydration ofdiscrete masses of moist material in hot oil, a tank adapted to containa body of hot oil, charging means for introducing discrete masses ofmoist material to be dehydrated into the tank at a level above the levelof oil therein, said charging means including a closed hopper underpartial vacuum and serving to evacuate be in communication with saidtank, feed means operable to deliver material from the hopper int-o thetank, evacuating means for placing the interior of the tank and saidhopper under partial vacuum and serving to evacutae vapors and gasesfrom the tank, and means for removing dehydrated material from the tank.

6. In apparatus of the character described for dehydration of discretemasses of moist material in hot oil, a tank adapted to contain a body ofhot oil, evacuating means for placing the interior of the tank underpartial vacuum serving to evacuate vapors and gases therefrom, means fordelivering a charge of said material to be dehydrated into an upperportion of the tank above the level of oil therein, discharge means at alower portion of the tank serving normally to close the same, pipingconnected to said discharge means for removing oil from both thedischarge means and the tank, and means within the discharge means abovethe lower end thereof serving to support dehydrated material depositedthereon when oil is removed from the tank and the discharge means.

7. Apparatus of the character described for dehydration of discretemasses o-f moist material in hot oil, a tank adapted to contain a bodyof hot oil, evacuating means for placing the interior of the tank underpartial vacuum and serving to evacuate vapors and gases from the tank,charging means for delivering a charge of said material to be dehydratedinto an upper portion of the tank, discharge means at a lower portion ofthe tank serving normally to close the same, said discharge meanscomprising a structure forming a vessel, screen means associated withthe vessel to support dehydrated material deposited thereon, and pipingconnected to the discharge means for removing oil from the tank, wherebyfree oil is separated from the discrete dehydrated masses.

8. Apparatus as in claim 7 in which said discharge means consists of anenclosing structure removably coupled to the lower end of the tank,together with a foramino-us centrifuge basket disposed within saidstructure, said centrifuge basket being disposed to receive dehydratedmaterial from the tank.

9. Apparatus as in claim 8 in which the piping connected to thedischarge means is connected to said structure at a point below saidcentrifuge basket.

10. In apparatus of the character described for the dehydration ofdiscrete masses of moist material in hot oil, tank means adapted tocontain a body of hot oil, evacuating means serving to apply partialvacuum to the tank means and to evacuate vapors and gases therefrom,means in communication with the tank means for introducing a quantity ofsaid moist material to be dehydrated into the tank means, a housing atthe lower end of the tank means and normally communicating therewith, aforaminous centrifuge basket disposed in said housing and adapted toreceive dehydrated material from the tank means, and means for removingoil from the tank means and the housing.

11. Apparatus as in claim 1t) in which the housing is separable from thetank means to facilitate removal of the dehydrated material.

References Cited by the Examiner UNITED STATES PATENTS 2,086,181 7/1937Bonotto 99-237 2,249,792 7/ 1941 Skinner. 2,286,644 6/1942 Pringle etal. 99-100 2,512,591 6/1950 Alexander 99-100 3,026,790 3/1962 Arvan99-336 3,118,741 1/1964 Faulk 34-9 OTHER REFERENCES Publication:Industrial and Engineering Chemistry, vol. 32, No. 2: pp. 154-149,February, 1940, Anhydrous Sodium Hydroxide Production byPartial-Pressure Evaporation by D. F. Othmer and I. I I acobs, Jr.

WILLIAM F. ODEA, Primary Examiner.

NORMAN YUDKOFF, Examiner.

1. IN APPARATUS FOR THE DEHYDRATION OF DISCRETE MASSES OF MOISTMATERIAL, TANK MEANS ADAPTED TO CONTAIN A QUANTITY OF HOT OIL, CHARGINGMEANS CONNECTED TO THE TANK MEANS AND OPERABLE TO INTRODUCE SAIDMATERIAL INTO THE TANK MEANS, EVACUATING MEANS FOR PLACING THE INTERIOROF THE TANK UNDER PARTIAL VACUUM AND SERVING TO EVACUATE VAPORS ANDGASES FROM THE TANK MEANS, SAID CHARGING MEANS HAVING A SPACE NORMALLYCLOSED WITH RESPECT TO THE ATMOSPHERE AND ADAPTED TO CONTAIN A QUANTITYOF MATERIAL TO BE INTRODUCED INTO THE TANK MEANS FOR DEHYDRATION ANDALSO ADAPTED TO BE IN COMMUNICATION WITH THE INTERIOR OF THE TANK MEANSWHEREBY SAID EVACUATING MEANS SERVES TO PLACE BOTH THE INTERIOR OF THETANK MEANS AND THE SPACE OF SAID CHARGING MEANS UNDER PARTIAL VACUUM,SAID CHARGING MEANS BEING OPERABLE UNDER SUCH CONDITIONS OF PARTIALVACUUM TO FEED MATERIAL FRFOM SAID SPACE INTO THE INTERIOR OF THE TANKMEANS, AND MEANS FOR REMOVING DISCRETE MASSES OF DEHYDRATED MATERIALFROM THE TANK MEANS.